Art of converting petroleum crudes



March 9, 1948.

E. H. RECORDS ART OF CONVERTING PETROLEUM CRUDES Filed Oct.- 13, 1945 jay. 1.

2.Sheets-Sheet l March 9, 1948. E. H.-RECORDS, 2,437,439

ART OF CONVERTING PETROLEUM CRUDES Filed Oct. 15, 1943 2 Sheets-Sheet 2 INVENTOR.

- E/nper econ/.5 1% k with Diesels.

Patented Mar. 9, 1948 CRUDES i ART OF CONVERTING PETROLEUM Elmer H, Records, Tacoma, Wash. Application October 13, 1943, Serial No. 506,109

9 Claims. (Cl. 196-59) This invention relates to. the art of refining hydrocarbon oils, or which is to say converting crude petroleums to pressure distillates, and for its general object aims to provid a heat-andpressure process, and an apparatus for working the same, capable of converting very nearly the entire volume of crude stock into products of distillation. The present applicationis a continuation-in-part of application for Letters Patent of the United States filed August, 18, 1941, Ser. No. 407,500, now abandoned. 7

Giving significance to the above-recited general object, it may be here stated that substantially the highest recovery of pressure distillates to which the refining industrylays claim is in the neighborhood of 65% by volume converted from petroleum or rock oil of the class termed paraifin base. In the handling of so-called asphalt base crudes, the recoveries are very appreciably less and conversion of as much as 45% by volume is considered excellent, stances shows up ass, tarryresiduum which has piled up in ever-increasing bulk about the various refineries, being practically worthless commercially and saleable as a, fuel oil only when mixed Disposal is thus effected at an actual loss to the refineries when the market value of the Diesel oil so introduced is weighed against the considerably lower return from the fuel oil,

which is sold in three grades of heavy, medium and light according to the Diesel c6ntent.- However, even disposed of in this manner, the market can take but a small part of the said residuum. The remainder continues to build up and'in its presence about a refinery, entirely discounting the petroleum loss which the same represents, is now a matter of very major concern, to the industry.

In my above reference totwo classes of petroleum crudes it will have been noted that my designation of the one as an asphalt base leaves some question as to the accuracy of the term, and it may be stated that Iam not alone in holding that the same is a misnomer and there is an increasing usage within the industry of the classifying terms green and ,black to identify, in the former instance, the petroleum crudes found in and about Pennsylvania, New York, West Virginia, Ohio, Kentucky, northern Louisiana, andv Canada, and, in the latter instance, the crudes from California and some sections of Texas. Mixed crudes showing the characteristics of both also are found, principally in Illinois, Kansas, Oklahoma, northern Texas, and Mexico, 7 only North America being considered. In support of The loss in bothinsaid mentioned'departure from nomials which i thepast have been generally accepted as having some basis in fact, it is now more or less ac'-, cepted that the two crudes are not unalike in molecular structure and presumptively must havebeen, substantially identical in the originating considering the areas in which the crudes occuras volcanic. If, therefore, green petroleum can be said to have been relatively freeoi'any volcanic influence, and the contrary true of black crudes, it may well be advanced as a tenet that the circumstance of the California crudes changing from a green to a black crude reflects a destruction in part of the molecular structure of the petroleum by a burning of the carbon radical, and suchpetroleum molecules ashave been come. paratively undisturbed in the various black deposit thus commingle with burnt carbon and varying proportions of sulphur in the presence of free hydrogen liberated by the burning of its aiiinitive carbon, It was my first thought in the course of developing the instant process that black crudes contained a considerable amount of the said burnt carbons, but in view of my present ability to arrive at very nearly the same recovery from the black as from the green crudes, this view has been necessarily revised and it therefore appears that blackcrudes have had but a minor portion of the constituent carbon atoms burnt outand that there are present in the crude stock a relatively high percentage of petroleum mole cules only partially eflected by the volcanic disturbances and which are in a state of instability verging on a break-down. This is to say that the carbon atoms so effected have a reduced afiinity, or presumably so, for the hydrogen with which the sameis combined, thus admitting to comparatively ready separation and burning in the I course of later refining, a premise which can be residuum from the working of green crudes gave every appearance of being not greatly dissimilar from the very heaviest of the black crudes. Although having a low sulphur content and being considerably more sludgy, both bodies reflected the presence of burnt carbon. The fact that there has been an increasing preference for the use of theterms greenfand black over paramn base and asphalt base? establishes thatv the similarity as between the objectionable substance of black crudes and the residuum from the green crudes has not escaped the research engineers of the industry, but whereas ithas been, the prevalent opinion prior to the advent of the present process that the burning out of a considerable portion of the constituent carbon is inescapable if the distillation is expected to obtain any appreciable part of the heavier-ends of the crude, my own approach to the problem was made with the convictionthat, the answer lay in,

wasthen a. logical assumption to conclude that.

the industrys substantially universalemployment of banks of hot tubes. through. which the crude was passed in. bringing. thev same to avaporizing temperature was placing the stockunder influences very similarto. that obtaining when. the crude enteredthe earth cracks and thereencountered the heat of the volcanic gases. From the fact that theprior refining procedures subjected all of the stock to therestraint. of these. confined.

tubes,.whereas.only. a .part. of the natural deposit entered. the fissures, the explanation, for the far greater destruction of the petroleum-by. a.burn ing out of the carbon atoms in industrialrefining appeared self-evident. I. further theerizedl that the carbon.- and hydrogen atoms, if. unlocked by theappliedheat reachinga. relatively intense point within the confines of the tubes and held in this unlocked state during the period, of

several seconds necessary to pass through the tubes, resulted in the burning of. the carbon before molecular re-establishment could take place. It seemedreasonable. in subjecting. the petroleum and especially the. heavier ends. thereof to, the necessarily intense heat. required. to. attain. the boiling points for vaporizing, that it was. only. necessary to allow the. molecules, to. escape from the point or points. of applied heata. fractional moment before the heat could attacka mutable carbon atom, and that this said carbon atom. would then re-establish. itself with. afiinitive hy drogen given azone. of temperature below charring. or coking. heat.

I first attributed the prior destruction of the very considerable part of the. carbon, atomsto the fact of the tubesbeing of. ahighly restricted nature, and working along this vein. constructed a relatively largebombinto which the stock. was sealed: and heated by a forge. This procedure showed'a considerably. higher recovery than had been. obtained from'accepted commercial opera tions, but itwas found upon removing the prod ucts for distillation. that some coking had set in about the heated surfaces, and it becameflogical to attribute this to the factual knowledge that the contained stock, even though to a lesser degree than exists in the use of a bank of hot tubes, was still trapped within heated walls and thus precluded from escape by thermal circulation for complete re-establishment of hydrocar bon molecules. I in consequence then resorted to the use of a tank laid. horizontally and inserted therein, to occupy positions paralleling the major axis and spaced from the inclosing walls, a pair of electrically heated rods, the petroleum stock being sealed within the tank and deriving its vaporizing heat from the internally applied rods. Numerous tests were run using this said tank and uniformly excellent results were obtained establishing to my satisfaction that the real answer layin the act of heating the petroleum stock through the instrumentality of the rods. Possessed, therefore, of a sound foundation principle-.-heating the oil by having the same lie in surrounding relation tothe vaporizing instrumentality as distinguished from application of heat to inclosing walls with resultant hot-spots from which the oil could not escape by its thermal circulation-progress was apparent but cognizance was had that the apparatus as then constituted was of questionable commercial practicability in that itsintermittent operation, interrupted by the time intervals in withdrawing each vaporized batch and re-stockingv the tank, preeluded large-volume conversion. I in consequence proceeded toward adapting my findings to a continuous-operation process, and which has been arrived. at in the course of extensive experiments carried on over a period of several years culminating in a highly. eflicient and currently operating plant having a 15-barrel per day capacity. Thefirst of a number of 50-barre1 plants to be installed in existingrefineries is now in course of construction, admitting to increased output either by battery installations or later production of alarger unit asthe industry may demand. 1

In the accompanying drawings wherein I have illustrated a plant embodying the teachings of my invention:

Figure 1 is a somewhat schematic showing thereof; Fig. 2 is a transverse vertical section on line 2-2 of Fig. 1; Fig. 3 is a longitudinal section taken toan enlarged scale detailing one of the internal heating rods which. will be hereinafter referred to as bayonets; Fig. 4 is a transverse vertioal section on line 44 of Fig. 3; and Fig. 5 is an end elevation of a bayonet representing the binding posts and showing a diagram of an energizing electric circuit.

Having reference to said drawings, I provide upper and lower pressure-tight cylindrical drums denoted by the numerals 55 and i and which. will be termed the still and the retort, respectively. The still is given the greater capacity and is. desirably mounted to have its major axis horizontal, while the subjacent retort occupies a sloping, plane, a declination of approximately 159 from the horizontal being found by experiment to attain the best results. Extending as connections between the two drums at each of the two ends are vertical pipes 8 and 9 fitted with valves I0 and I I, respectively. Such Valves, as with the other valves in the system hereinafter referred to, are of a gate character to assure a rectilineal course for the travel of the petroleum stock, distinguished from. globe valves and the relatively tortuous paths characteristic thereof.

Introduced in said still and in the retort are a the still as being equipped with two and the retort with four such bayonets-which are supported by a head wall of the related drum and carry very nearly the full length of the latter, being in each instance disposed in paralleling relation to the major axis and occupying positions relatively remote from the inclosing drum wall. Each said bayonet, denoted generally by I2, is. constituted of an insulating center core l3 of porcelain or the like longitudinally channeled along the periphery to present seating grooves for a pair of looped resistance wires [4 and IS, the loops l4 and I5 lying at the inner end of the :core and the opposite extremities, or which is to say the free ends of the paralleling branches, being joined to binding posts, as l6 and I! for the wire 14, and i8 and [9 for the wire l5, connected in parallel to a source of electrical energy stepp d up from line current by a suitable transformer. I desirably embed the said cores in cement or the like, encasing the body in a seamless steel tube 29.

The system .is arranged to be charged by filling the retort and bringing the level within the still to approximately three-elevenths of its capacity, and this chargepreheated by its passage through an intervening heat chamber 2l--is taken from a crude-supply reservoir 22 through a pipe 23 and pressure-injected into the still under the influence of a pump 24, the injection being in the form of a spray projected from an atomizing nozzle 25 which lies above'the liquid level of'the still and at the end thereof corresponding to the high end of the retort. 'It will be understood, following the initial charge and subsequent evolvement of products of vaporization as the same is brought within the retort-and-still system to a condition of working temperature and pressure, that a replenishment of depleted stock is made at periodic intervals having recourse to a level gauge 28 with which, together with pressure and temperature indicating instruments 26 and 21, respectively, the still is equipped. While the replenishing step has been manually governed, automatic control is entirely feasible.

Describing the structural nature of my retort in more particularity, it will be seen that the lower end thereof projects in a longitudinal direction somewhat beyond the still or perhaps more properly stated, somewhat beyond the delivery point at which circulating stock enters the retort from the 'downi-low pipe 8, and there is provided at the base of this said projecting portion a sump dependency, as 1', having 'afunnel bottom from which a drop-pipe 30 connects with the head end of an upright tank 3| similarly formed with a funnel bottom and which I term a decantation vessel. A take-off pipe 32 leads from the decanting chamber into a cooler 33 composed, say, of coils surrounded by circulating water, and thence carries by pipe 34 to a filter 35 wherefrom the filtrate is either pumped 0r gravity-Jed through a pipe 35 into the storage reservoir 22 for later return to the still, mixing in the reservoir with crude stock.

In furtherance of the decantation vessel, the two pipes 30 and 32 are fitted with valves 31 and 38, respectively, and the vessel itself is equipped with a petcock 4B. The arrangement of sump and decanting chamber, and the indicated controls constituted of the two valves and the petcock, would seem to be of considerable import to the eflicient performance of the-system, sediment containing sand and the like together with burnt carbon where present in the crude being held in a 6 relatively quiet state as the same works along the sloping bottom of the retort into the sump, and being drawn of! together with high-viscosity heavy ends of the oil by the instrumentality of closing valve 38 and Opening valve 31 and the v petcock. In addition to sedimentary solids and semi-solids, water, also frequently obtains in crudes and in working the present process, rather than emulsifying, with the oil as evidenced on occasion in prior refining procedures, such water is found to gravitate to the bottom of the sump, thereafter blowing oil. as a steam through the open petcock as valve 31 is opened. As oil shows through the petcock 1'0110Wing the steam escape, the vessel contents are passed to the cooler by closing valve 31 and opening the valve 38, an

atmospheric head being obtained through the open petcock.

Reverting to the circulation within the still and the retort as the petroleum stock is treated therein for conversion to a vapor state, and looking to a more advantageous circulation than can be obtained by thermal movement, there is provided a pipe-line 4| applied as a by-pass about the up-fiow pipe 9. In this by-pass is a pump 42. The-by-pass leads from the lower limit of the retorts head end and thus, by relative isolation from the rising vapors presented to the admission end of said principal pipe 9, is fed by light ends of the stock in a liquid state to the exclusion of evolved vapors. The by-pass enters the still below the liquid level of the latter and is caused to eject its pressure column of oil through a horizontal nozzle 43 which immediately overlies the outlet from the said principal pipe, and there is thereby developed an inductive pull accelerating the'velocity of travel of the fluid stream rising through pipe 9, the admixed vapors being in consequence caused to pass rapidly upwardly by their travelling momentum through the liquid contents of the still into the vapor dome-which, as hereinbefore stated, is described within and constitutes the upper eight-elevenths of the stills volumetric capacity.

Leading off from the upper limits of said vapor dome the still connects through a valved pipe 44 with a U-trap 45 from whence the vapors feed to a condensor 46 and therefrom to a tank (not shown) for the products of distillation. The .particular significance of said U-trap may be here explained by stating. that the break-down of the highly complex petroleum oils evolves certain gases evidencing a state of transciency in their molecular structure, which are relatively noncondensi ble and which, lacking the presence. of the trap, carry through and escape as gases. These gases are quite light, hence are readily held :back by the trap While the comparatively heavier condensible vapors traverse the same, and being characterized by transiency tend to exist only momentarily in various stages of'molecular com- 'bination, their chameleon-like nature ultimately causing the same to become structurally rearranged as a heavier and condensible vapor in the atmosphere of successively presented stable gases, thereupon proceeding with the latter through the trap and condensing into pressure distillates.

The process is believed to be clear from the introductory passages wherein consideration was had of previous practices involving ceiling hotspots and an analytical compariso drawn between such procedures and my employed bayo brought out the functional significance of the parts.

I am not unawarethat the results may, at least in part, be attributed to the peculiarities of elec-'- tricity circumstantial to my bayonets, namely the mamier of construction and application, and along this vein it might be advanced that there is present a catalytic effect of force-field emanations generated as part of the normal phenomena of current-carrying conductors so contained as to have properties of inductance, impedance, capacitance, and interactance. The accomplishments of a said catalysis ascribed to electrical phenomena would be beneficially increased by my particular arrangement including, through hysterisis, a very high temperature in the surrounding armor of the heaters, diminishing correspondingly with its degree of removal from the originating resistance wires I4 and IE but yet producing emanations of sufiicient density to efiectuate a hysterlsis-induced heat of below-coking intensity in the steel shell of the retort or still, as the case may be. Whatever may be the complete explanation, there is this to say in respect to the process, the results can hardly'be disputed, consistently showing recoveries so far beyond any prior expectations of the petroleum industry as to have been labelled fantastic.

I furtherance of these said results, and selecting runs supported by certificates of leading petroleum laboratories, refinement of Santa Maria crude, 16.2 gravity, A. P. I. 60 F'., with a 4.42% sulphur content, produced at 98.5% recovery of pressure distillates, considered by volume, containing 0.7% sulphur and 42.9 gravity. This, compared with a prior customary recovery of 45% by volume with the residue reflected in a semi-solid residuum heavy in burnt carbon, would appear as strong evidence in support of the statement, hereinbefore made, that there has been in nature only a slight amount of the carbon radical "burnt-out of the petroleum which the industry terms a black crude, and that the principal damage to the hydrocarbon molecules occurs from the more pronounced destructive steps which have been heretofore practiced in refining and which, in addition to coking more susceptible carbon atoms which have been partially effected by volcanic gases, burns out other carbon which had been completely free in nature of the adverse influence of volcanic disturbances.

Likewise indicative is the recovery from a run of Wyoming crude blended 50/50 with old crank case oil, giving a 19.7 gravity reading, and from which the present process obtained a 97% by volume pressure distillate showing of 48.3 gravity.

Working with a Wyoming crude from the Oreg-on Basin, 20.5 gravity, a prolonged run recovered 96% by volume of pressure distillate showing 48.2 gravity,

On a run performed for Standard Oil from the Gate Ridge area of California, considered a lowgrade black crude with a, 13.9 gravity reading and high sulphur content, a surprisingly high return of 52.9 gravity pressure distillate was obtained, 95% by volume with a drop-in the sulphur content to .62%.

It is one of the peculiarities of the results that, aside from a higher gravity pressure distillate in the working of green over the black crudes, the percentage by volume of recovery is substantially the same, exemplified by a run of Cut Bank crude from Montana, 30.9 gravity, obtaining a pressure distillate end product of 57.9 gravity with 1% loss.

comprehended in the tests which I have conducted are a number performed with marketed lubricating oils toward ascertaining to what extent the same could be converted to light ends, vaporized, and the said vapors condensed to a relatively high-gravity end product. By way of example, an S. A. E. 50 Texaco oil, treated in my refining plant, showed a recovery of 97% by volume of 43.9 gravity pressure distillate. This character of petroleum stock is not unlike natural crudes, and. the results--knowing the recoveries from the process as applied to the latternot unexpected, but I have also established by conclusive test-runs performed on the residuums from other refineries that it is also possible to obtain high-gravity returns of considerable quantity from this type of previously unworkable stock, 14.4 gravity straight-run residuum supplied by Richfield Oil showed a pressure distillate recovery of very nearly the entire body in 65 octane 60.9 gravity oil, the plant in this instance recovering from the residuum 97% by volume of this said high-gravity distillate. While other runs on residuum stock have consistently showed extremely high recoveries well over by volume, the Richfield recovery seemed to be somewhat out of line, and its explanation might very possibly lie in the assumption that the originally worked crude had been subjected to a heat of comparatively low intensity, which is to say that the same had been treated primarily toward recovering from the complicated mixture of hydrocarbons present only the compositions of lower boiling points, leaving the heavier ends relatively undisturbed and sacrificing a greater recovery in favor of high-octane gasoline, freed of the necessity for later separation. The point remains, however, that Richfield considered this particular residuum to have been worked out beyond any profitable recovery of the contained hydrocarbon formulations, and not unnaturally evinced very considerable excitement in the presence of a factual showing, certified to by certificate of a petroleum laboratory recognized throughout the industry, that this same residuum and in very nearly its entire volume represented a source of pressure distillate comparable to third-structure gasoline.

An accomplishment of no little moment, and which I have given no prominence to in the course of the foregoing, is the ability, and which I find to .be inherent to the process, of handling high-sulphur crudes and largely eliminating the objectionable sulphur from the pressure disti-1- late. Treated stock such as the above-mentioned Santa Maria crude high in sulphur content has been consistently found to derive a pressure distillate showing less than 1% sulphur content. To reiterate and. by way of example, the laboratory returns on the said Santa Maria crude compared with their analysis, of the pressure distillate show a reductlonfrom 4.42% to 0.1% sulphur content. This diminution is typical of the reductions which I have obtained in the handling of black crudes, green crudes being comparative as, for example, the Cut Bank run to which I have referred reduced the sulphur content from 1.13% by weight in the crude to 0.12% in the distillate. Thus, the present processexcepting in the working of crudes running well over 4% in sulphur-obviates to all practical purposes any need for the introduction of a desulphurizing mixture such as I describe and claim in my U. S. Letters Patent No. 2,232,971, issued February 25, 1941.

In furtherance of the above it may be stated that the actual showing of sulphurin the residue from the filter is b'ut'a small part of the total, andit becomes self-evident that the bulk of the sulphur content carries oil as a vapor. However, I have no presentfanswer to their actual nature as the plant is completely free of the odor of sulphur, hence assumedly do'not clear the condenser and escape as gas, --It is of considerable interestto point out that there appears to exist in the pressure distillate a character of formulation foreign to customary gasoline and which I amunable to give name to. Nor have the laboratory engineers with whom I have frequently discussed the matter been enabled to isolate or identify such. It is their consensus thatsulphur may very possiblyexist in a locked state-I incline to alike view-but that'rather than-being a detriment the gasoline obtained possesses marked advantages as an engine fuel over likegravity distillates from other refining processes.

The description of the process is hardly complete Without reference to the temperature and pressure employed, and my best results have been obtained under readings of 630 F. and 200#, respectively. Having brought an initial charge up to this temperature and pressure, and putting the pump 42 in operation, a constant output of pressure dlstillates may be maintained with continuous controlled input of replenishing stock, the sump I being emptied periodically.

In describing my process and the novel apparatus which I now prefer to employ in practicing the same, there has been no effort made to point out departures which might be resorted to and which will be largely self-evident having knowledge of the invention. It is the intention that no limitations be implied, and that the hereto annexed claims be read with only such restrictions as are expressly introduced thereto. The term petroleum as herein employed, and references to crude as pertaining to the stock with which I charge the system is to be understood as including all applicable hydrocarbon bodies.

What I claim is:

1. The new method of treating petroleum crudes to substantially eliminate destructive coking in heat-and-pressure conversion into products of distillation, and which consists in charging a still with a stock of the crude hydrocarbons to approximately three-elevenths of the volumetric capacity, passing the stock from the still into the lower end of a subjacent inclined retort of wide expanse and within the retort subjecting the stock to heat of internal origination removed a material distance below the ceiling wall of the retort and of sufiicient intensity to boil the heaviest ends, giving access by thermal movement for return of evolved vapors from the upper limit of the retort into the still, passing off and condensing the vapors, collecting in the vapor dome described above the liquid level of the still, periodically decanting heavy ends and commingled sediment from the lower limit of the retort, filtering the body so removed, and returning the filtrate to the still and additionally supplying replenishing crude to the latter as necessary to maintain the liquid level within the still, light liquid ends being pumped from the retort and, as an aspirator, pressure-injected into the still over the point of delivery of the vapors thereto for accelerating the velocity oftravel of vapors passing from the retort into the still.

2. The new method of treating petroleum crudes to substantially eliminate destructive coking in heat-and-pressure conversion-intoproducts oi distillation, and which'consists in charging a still with a stock of the crude hydrocarbonsto approximately three-elevenths'oi the volumetric capacity, passing-the stock from the-still into the lower end of a subjacentfinclined-retort and within and throughoutthe approximate entire length of the retort subjecting the stock to heat of in ternal origination and of sufiicient intensity to boil the heaviest ends, passing evolved'vapors by inherent thermal rise from the substantial upper limit of the retortback to thestill and coincidently drawing off light liquid ends from the retort and pressure-injecting the same into the still,

passing ofi the vapors collecting-in the vapor dome described above the-liquid level of the still and condensing the same,'periodically decanting heavy ends and commingled sediment from the lower limit of the retort, filtering the body so removed, admixing the filtrate'with fresh crude, and injecting the latter as an atomized spray of replenishing stock into the vapor dome of the still in quantities necessary to maintain the liquid level within the latter.

3. The method of claim 2 including preheating the replenishing stock without bringing the same to a boiling state in advance of the delivery of the same as an atomized spray.

4. The method of claim 2 including subjecting the vapors passed ofi from the vapor dome to repression by causing the vapors to follow a U- path and, .in such travel, pass through a body of liquid collected as a condensate of the vapors in the bend of the U.

5. The described plant for converting petroleum crudes into products of distillation and comprising, in combination, a still arranged to be charged with crude stock to a portion orny of its volumetric capacity leaving a vapor dome thereabove, a retort of comparatively wide expanse disposed sub acent to the still and inclined from the horizontal to an approximate 15 angle, said retort presenting a sump at its lower limit, a down-flow connection at one end of the still having its inlet below the liquid level and emptying into the lower end of the retort at a point forwardly advanced beyond the sump, an up-fiow connection from the extreme upper limit of the retort and returning to the other end of the still discharging below the liquid level therein, heating bayonets for the still and for the retort submerged within the liquid therein, a second and pump-equipped fluid-flow connection from the retort to the still extending as a by-pass about the first-named up-fiow connection and having its inlet at the upper end of the retort below said first-named up-fiow connection, a condensor, a draw-ofi line from the vapor dome to the condenser, a cooler and a filter connected in series, means for drawing ofi heavy ends of the treated crude with commingled settlings from the sump and delivering the same to the cooler, and means for commingling the filtrate with fresh crude and ejecting the same as an atomized spray into the vapor dome of the still as needed to maintain the liquid level within the still.

6. Structure according to claim 5 having a U- trapintroduced in the vapor draw-ofl? line to lie in intervening relation between the vapor dome and the condensor. V

7. Structure according to claim 5 having a nozzle outlet from said by-pass connection submerged in the liquid within the still and disposed in such relation to the emission end of the first-named up-iiow connectionas to constitute an aspirator therefor giving an accelerating lift to the evolved I vapors rising through the latter.

8. Structure according to c1aim 5 in which the heating bayonets are comprised of resistance rods of U form receiving circuit-closing electric current through the free extremities of the two branches, and having a high-permeance metal shell insulated from and encasing the rods. 7

9. Structure according to claim 5 providing a decantation vessel disposed to occupy a position below the sump and above'the cooler, and having gravity-flow connections to its head end from the sump and from its bottom end to the cooler, said decantation vessel being equipped with a petcock, and valves in said gravity-flow connections arranged to be opened in alternation and in con- .junction with a control of the petcock to obtain an interruption in the travel of the draw-oft from the sump to the cooler. V

ELMER H. RECORDS.

REFERENCES CITED The following. references are of record 1111118 file of this patent:

UNITED STATES PATENTS Smith (II) Feb.-26, 1935 

